There are trolls. There is a man who hunts them. This will be lure enough for most fantasy addicts, but André Øvredal’s movie has wittier ideas up its sleeve than the average “mock-doc” shocker, a genre it transcends through sheer originality. It’s halfway to a comedy, except that the trolls are the opposite of chummy, and look as though they could wipe out whole villages with their bad breath alone. Imagine John Prescott, basically, and then give him two extra heads. The set-up’s pretty ordinary – some student filmmakers wade into deep, deep water investigating apparent bear rampages, and end up scurrying around in wobbly-cam panic when something 200ft high clocks them in a forest. The alleged hunter they’re stalking (Otto Jespersen) doesn’t mess around – he has a suit of homemade armour for emergencies, patrols bridges, and drives around with huge spotlights ready to petrify his quarry. So many details are funny, from the types of troll – beware the Ringlefinch, giggle as you run from a Rimetosser – to the notion of a government conspiracy to cover up troll activity. It’s the God-fearing these things are after – one closet Christian breaks down and confesses in a cave. What about Muslims? No one quite knows. One thing’s for sure – it’s certainly the most appealingly bonkers effects blockbuster ever to come out of Norway.